76 entries under hard topic. ×

2
impenetrable(adjective, set, tough, firm)
2
impermeable(adjective, set, tough, firm)
2
inelastic(adjective, tough, solid, rigid)
2
inflexible(adjective, set, strong, tough)
2
nonporous(tough, solid, rigid, inflexible)
2
rigid(adjective, set, strong, complete)
2
set(verb, adjective, strong, tough)
2
solidified(verb, adjective, set, tough)
2
substantial(adjective, set, strong, tough)
2
unyielding(adjective, set, tough, firm)
1
biting(adjective, strong, great, severe)
1
bold(adjective, sharp, bright, high)
1
close-grained(adjective, set, tough, firm)
1
congealed(verb, adjective, set, tough)
1
effective(adjective, sharp, bright, regular)
1
hardened(verb, adjective, set, strong)
1
hefty(adjective, strong, tough, powerful)
1
hot(adjective, sharp, bright, intense)
1
husky(adjective, strong, tough, vigorous)
1
impervious(adjective, set, tough, solid)
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APASmart Define. (2015). concentrated thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/concentrated/thesaurus/synonyms
ChicagoSmart Define. 2015. "concentrated thesaurus" https://smartdefine.org/concentrated/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, concentrated thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/concentrated/thesaurus/synonyms>.
MLASmart Define. "concentrated thesaurus" 10 April 2015. Web. 25 September 2026. <https://smartdefine.org/concentrated/thesaurus/synonyms>